Phonograph



B. E. COVER Jan. 17, 1928.

PHONOGRAPH Filed July 22, 1922 lio Patented Jan. 17, 1928.

PATENT OFFICE.

.'BEBXEY E. COVER, 0F CHICAGO, ILLINOIS.

rnoNoGnAPrr.

Application 1aed July 22, 1922. serial No, 576,691.

This invention relates to phonographs and has for its principal objectto amp ify the vibrations set up in the stylus bar by a phonographrecord and transform them into electric waves capable of operating atelephone or other sound receiver.

A further object of the invention is to provide an electrical reproducerfor phonographic records embodying the principles of the microphone. y

A further object of the invention is to provide a reproducer in which astylus bar mechanically operates a plurality of microphones, from whichit is electrically insulated.

Further objects of the invention will become apparent as the descriptionis read in connection with the accompanying drawing illustrating aselected embodiment of the invention, andin which Y Fig. 1 is a planview of a reproducer embodylng the invention with the cover removed;

Figs. 2and 3 are sectional views taken on the lines 2-2 and l3 3respectively of Fig. 1 and Figa 4 is a sectional view on the line 4-4 ofFig. 2.

Referring to the reference numerals on the drawing, indicates a base,here shown as made of stamped metal and comprising a disk having acylindrical flange 11 at its periphery and a tubular flange12's`urrounding its central opening. FlanUe 12 is here shown. as aseparate cylinder reduced to form a shoulder 13 and upset at 14 tosecure the flange to the disk. A plurality of bosses 15 are stamped orpressed up from the disk -to which are secured posts 16 by screws 17.

Preferably the posts are insulated from the base by means of washers 18and the tube 19 which prevent contact of the posts and the screws withthe base. In the embodiment shown, four of these posts are electricallyconnected in pairs by strips 20 lying between the upper washers 18 andthe bottoms of the posts 16 and securely clamped by the screws 17 Eachpost is equipped with a transverse bore 21 which receives the shank 22of a carbon cup member 23 here 'shown in the form of a disk, having aperipheral flange 24. A fixed carbon electrode 25 rests against each ofthese disks and is secured in place by 'a nipple 26 threaded into theflange 24 and bearing against the periphery of the electrode. Within thenipple 26 is an annular ring 27 of loose asbestos libre surrounding asuitable quantity of granules of conductive material 28 such as carbonor coke. A movable electrode 29 cooperates with the fixed electrode 25of each carbon cup to'press and release 4the granules and thereby varythe conductivity ot' .the cups. The movable electrode 29 lies against adiaphragm 30 of mica or other suitable material which is held in placeby a threaded cap 3l. A screw 32 passes through each electrode 2S),diaphragm 30 and into a diaplnagm plate 33 which has a tubular shank 34.The shanks 34 of opposed microphones are of slightly different length asimlicated'in'Fig. 3 and screws 32 vary in length to correspond. Thelonger screw 32 passes through one end of a connecting bar 35 here shownin Fig. 1 by which the two pairs of microphones are connected foroperation in unison, facing one another, and with theV movableelectrodes substantially parallel to each other. The middle portion ofthis bar is enlarged as indicated at 36 and perforated to receive thethreaded end 37 of a stylus bar 38 pivoted on a pin 39 passingthroughaligned openings in the internally flanged liner 41 secured in the tube12 by the set screw 42. In order to insulate the stylus bar from themicrophones, I provide the washers 43 and 44 and the sleeves 45 ofinsulating material which prevent contact between the stylus barv andthe connecting bar 35. For convenience thel sleeve 45 is made longenough to receive the perforated end 46 of a connector 47 to which thecable 48 isy attached. The strips 20 are provided with the arms 49 towhich are attached cables 50 and 51. The cable 50 is therefore connectedwith the fixed electrodes of two of the microphones While 51 isconnected to fixed electrodes of the o posite two microphones and thecable48 is the common for the movable electrodes of all the microphones.

The stylus bar 38 is preferably equipped with a bushing 52 tightlyfitted therein and reamed to a slight taper corresponding with the pivot39. It is very important that the bearing of this pivot be free from anylost motion that will result imnoise or rattling when the stylus barvibrates.

The base 10 is preferably fitted with an arched cover 53 secured'to theflange 11 by screws 54 or other suitable fastening. This coverpreferably .carries a fitting 55 havin suitable passages for the cables48, 50 an 51. I prefer to make this cover of perforated meta-l as"indicated, but it may be of any suitable form.

When the stylus bar 38 is vibrated by the stylus 56 runmngin the grooveof a phonograph record, the upper end of the stylus bar will reciprocatethe movable electrodes of the microphone and produce alternatln electricwaves. VThe magnifying effect o the microphones will cause these wavesto be of much ygreater amplitude than the vibrations of the stylus bar.Consequently they can be used to operate a telephone or other receiverdirectly. For some purposes, it will be desirable, however, to fultheramplify t-hese .waves which may be done in the manner indicated in myco-pendin-g application, Serial No. 581,572, filed August 14, 1922,01*in any other desired way.

The arrangement illustrated shows how a plurality of microphones maylie-connected to be operated by a single stylus` bar and will besuiicient to teach those skilled in the art how to make use of anysuitable number that may be required by particular service.

The insulated joints between the posts 16 and the base 10 and betweenthe stylus bar 38 and the connecting bar 35 confine the current to partslying within the cover 53,`

so that there is no danger of either fire or shock from the use of theapparatus.

By mounting themicrophones in the posts 16, as shown, andsecuring themin place by screws or other suitable fastening means, the several cupscan be readily located and ad justed to operate evenly with themovements of the connecting bar 35. This arrangement also permits thecups to be quickly ,and easily dismantled for inspection,4 repair,

phones, a stylus bar extending through said connecting bar and rigidlysecured thereto, and means for' insulating said stylus bar from saidconnecting bar;

2. In a reproducer, a pair of microphones spaced apart and facing` oneanother, each microphone comprising a fixed electrode and a movableelectrode, the movable electrodes of said microphones being oppositelydisposed and substantially parallel and coaxially connected together tooperate in unison, slidable mounting means for said microfixedelectrodes, and a common conductor connected to said movable electrodes.

4. In a reproducer, a. plurality of pairs of microphones, themicrophones 1n each pair being spaced apart and facing one another andeach microphone comprising a fixed electrode and a movable electrode,the movable electrodes in each pair being oppositely disposed andsubstantially parallel to each other and connected together to operatein'unison, a pivotally mounted stylus bar between the microphones, andmeans connecting said stylus bar to the movable electrodes in each pair.

5. In a reproducer, a plurality of pairs of microphones, the microphonesin each pair. facing one another and each microphone comprising a fixedelectrode and a movable electrode, the movable electrodes in each pairbeing substantially parallel to each other and connected together tooperate in unison, a,v pivotally mounted stylus bar, means connectingsaid stylus bar to the movable electrodes in each pair, a pair ofconductors, one fixedelectrode of each pair of micro hones beingrconnected to one of said con uctors andthe other fixed electrode of eachpair being connected to the othercof said conductors, and a commonconductor connected to all of said movable electrodes. 106

6. In a reproducer, a pair of posts, a microphone supported on eachpost, said microphones being spaced apart'and facing one another andbeing substantially parallel to each other, each microphone comprising a110 fixed electrode and a movable elect-rode, said movable electrodesbeing oppositely disposed, intermediate means connecting said movableelectrodes. and means for adj usting` said microphones in said posts tovary the 115 distance therebetween.

7. In a reproducer, a plurality ofpairs of microphones, the microphonesin each pair facing one another and each microphone comprising a fixedelectrode and a l movable electrode, the movable electrodes u in eachpair heilig substantially parallel to each other and connected togetherto operate in unison, a pivotally mounted stylus bar, and meansconnecting said stylus barv to the movable electrodes in cach pair.

miam-:Y E. covinz.4

